In large-scale underground mining operations, for instance of coal, it is standard to use conveyors that incorporate very long endless chains, and to use similar chains to convey back and forth the plow that actually cuts material from the face. Such chains are subjected to considerable stress and work in gritty conditions where they are subjected to great wear.
A connecting link with a pivoting and lockable side piece or a double-clevis link is used to join together the ends of the chain into the desired endless loop. Such links are actually the weakest link in the chain, which itself is subjected however representing an annoying maintenance task and unproductive do time for the machine in question.